1. Field of the Invention
The present invention relates generally to a method and system for providing Greenwich Mean Time (GMT) in a mobile broadcasting service based on Digital Video Broadcast-Handheld Convergence of Broadcast and Mobile Services (DVB-H CBMS), and more particularly to a method and system for providing GMT to a mobile terminal through a communication network.
2. Description of the Related Art
There are continuous requests for the mobile communication market to create new services through recombination or integration of existing technologies. Today, with the development of communication and broadcasting technologies, either a conventional broadcast system or a mobile communication system reaches a phase of providing mobile broadcasting service through a portable terminal (or a mobile terminal) such as a mobile phone or a Personal Digital Assistant (PDA). While engaging with sharply increasing demands of users in conjunction with this potential, practical market demand for multimedia services, strategies of service providers who intend to provide new service in addition to an existing voice service, and interests of Information Technology (IT) companies that reinforce mobile communication businesses to meet the demands of users, convergence of the mobile communication service and the Internet Protocol (IP) has been settled as a main current of next generation mobile communication technology. Further, commercialization and standardization of the mobile broadcasting service that provides broadcasting services to mobile terminals are actively under way.
For example, commercial services based on the DVB-H CBMS standard have already been provided in Italy, and commercial services based on the Open Air Interface (OAI) standard led by Nokia are being provided in Vietnam. In addition to these standards, there are various standards associated with the mobile broadcasting service, such as the S/T Digital Multimedia Broadcasting (S/T DMB) standard, the MediaFlo standard, the DVB-Satellite services to Handheld (DVB-SH) standard, the Open Mobile Alliance Mobile BroadCAST (OMA-BCAST) standard, etc. In particular, the DVB-H CBMS, DVB-SH, Nokia-OAI, and OMA-BCAST standards have considerable common characteristics in that they make use of a DVB-H network for a subordinate transmission end, and that they are required to receive Electronic Service Guide (ESG) data in order to provide the mobile broadcasting service. However, these standards show a difference between data models used in the ESG data between elements and attributes used in each fragment.
The providers who intend to provide the mobile broadcasting service using the DVB-H network have one of the providers' common requirements, which is to provide the ESG data using the broadcasting network and the communication network at the same time. Particularly, the OMA-BCAST standard provides a method of receiving the ESG data, as well as a method of providing the ESG data in various fields in combination of the broadcasting network aid the communication network. Thus, the ESG data should include broadcasting content provided through the broadcasting network, as well as guide information about broadcasting content provided through the communication network. In conjunction with transmission of the ESG data, standardization is under way.
In general, ESG data is divided into a plurality of fragments when transmitted to a mobile terminal in the mobile broadcasting service, and can be transmitted through two processes. An announcement session shows how the fragments are divided and over which network the fragments are transmitted, and transmits Internet Protocol (IP) address information or Uniform Resource Locator (URL) information that is required to receive the fragments. Thus, the information, which is required to receive the ESG data, is obtained through the announcement session. On the basis of the obtained information, an ESG data session receives ESG fragments. The DVB-H or DVB-SH standard defines an ESG bootstrap session, in addition to the two aforementioned sessions. This ESG bootstrap session provides a method of selecting a specific ESG data provider in the case in which the ESG data provider is plural in number, and provides an ESG access descriptor.
Meanwhile, in order to enable the mobile terminals to execute the mobile broadcasting service, the mobile terminals must provide time synchronization to the broadcast network and the communication network, which provide the mobile broadcasting service. Thus, the mobile terminals receive Program Specific Information (PSI) or Service Information (SI) information through broadcast stream transmitted over the broadcast network, and then receive Greenwich Mean Time (GMT) using a Time and Data Table (TDT) of the received PSI or SI information.
However, the conventional mobile broadcasting service does not provide GMT through the communication network, and thus the mobile terminals cannot obtain GMT through the communication network. For this reason, in cases in which the mobile broadcasting service is conducted through the communication network while no broadcast signal is received, the time synchronization must be provided between the mobile terminal and the broadcasting service system.